Preparation and Mechanical Property of Alumina Fibers Reinforced Thin Architectural Ceramic Plate

The fibers reinforced thin architectural ceramic plate of 900 mm×1800 mm×2.5 mm with high mechanical property was prepared by a fast-sintering method with a controllable fiber dispersion process. The effects of ball-milling time to the dispersity, average length-diameter ratio and microstructure of alumina fibers were investigated respectively. Meanwhile, the alumina fiber contents to the volume density, water absorption, phase transformation and microstructure of the thin ceramic plate were researched. It is found that the two-steps ball-milling process can control the average length-diameter ratio of the alumina fibers effectively and achieve a well dispersion mixture of fibers and ceramic powders, the fast-sintering method is beneficial for the protection of fiber/matrix interface. The trend of the volume density and bending strength increases with the fiber content from 0 wt% to 5 wt% and then decreases with the fiber content from 5 wt% to 15 wt%. The bending strength of this composite reaches the maximum value of 146.8 MPa with the fiber content is 5 wt%, which is corresponding to the strengthening of alumina fibers and the formation of mullite crystallization in fiber/matrix interface and matrix during the fast-sintering process.

Ablation of Al2O3f/Al2O3 Composites Under Oxyacetylene Torch Flame

Continuous alumina fibers reinforced alumina matrix composites (Al2O3f/Al2O3 composites) were produced by following the sol-gel process effectively, while the ablation behavior was analyzed and compared by means of oxyacetylene torch flame test. The results suggested that Al2O3f/Al2O3 composites showed excellent ablation resistance, but no obvious cracks, pits or holes after ablation. The mass and thickness of the sample were barely changed after ablation. After ablation for 120s at 1800℃, the surface morphology of composite material showed no significant change. With the increase of ablation temperature, there were visible signs of high-temperature and high-pressure gas erosion found on the surface of composites. Then, the molten black material began to appear on the surface, and the delamination phenomenon occurred finally. After ablation at 2200℃, the surface of composites became uneven, manifesting large-scale black molten particles, and the area affected by ablation was increasing obvious.

Study of ice composites reinforced by nanosized alumina fibers using nuclear magnetic resonance methods

The aqueous suspensions of nanosized alumina fibers and ice composite materials based on them were studied using Pulsed-Field Gradient NMR and Magnetic Resonance Imaging methods. It is shown that the introduction of nanofibers does not lead to noticeable structural effects in suspensions in the concentration range of 1 - 10 wt. % Al2O3. It was found that a high concentration of filler significantly changes the morphology and texture of the ice matrix in composites: it becomes more homogeneous, with a high degree of continuity; when the melting front passes through, internal regions of thawing or failure of the integrity of the composite are not visualized. Yet the introduction of nanofibers into ice composites has a weak effect on the quantitative dynamics of heat transfer processes, making the rate of freezing/thawing front propagation to be similar in different samples at comparable temperatures of the process.